I, uh, humm...
I have a CharBroil gasser that I vacuum out the bottom now and then. Because drippings tend to build up and can cause a flare up if new grease drips on them.
So that's what I do. There isn't any build up above the grates.
Mostly Chicken and Baby Back Ribs gets cooked in the gasser.
My smokers are electric and I basically use them as a temperature controlled outdoor smoking oven, they are highly modified from original. Because I do more cold to warm smoking, and the smoke goes from a box through 96" of aluminum tubing to cool it and condense out any creosote or ash from the smoldering pellets or sawdust.
The creosote tends to flake itself off inside the box where the pellets/dust burn.
But inside the oven box only has a patina of smoke, no heavy build up. Very thin blue smoke emerges when in use.
I smoke for curing and flavor, not to cook.
The ash from that generally gets dumped from the tray the next day.
I mostly cure and smoke Bacon and Salmon.